Subscribers of communication services are grouped into user segments based on for example subscription types but may also be grouped into user communities due to various preferences as social networks, hobbies, demographical profile etc.
With more and more personalized offerings and subscription in the mobile networks, it becomes increasingly important to tailor the information presented to the end users based in such groupings. For example, if the operator targets a specific segment of users in a certain locality to receive a free coffee at the local café, only the intended end users should see the message. If other end users see the message they might want to use the offer as well and the operator will either get complaints or higher cost for the campaign.
Various mechanisms exist to communicate information to a user in a communications network such as a mobile network, e.g. Global System for Mobile Communications GSM or Universal Mobile Telecommunications System UMTS. These include for example Unstructured Supplementary Service Data USSD, Short Message Service SMS or Internet email.
All these mechanisms are unicast transmission mechanisms, i.e. the sending of messages to a single network destination identified by a unique address.
Many applications requiring transmission of information to be mass-distributed are too costly to be conducted with unicast transmission since each network connection consumes computing resources on the sending host and requires its own separate network bandwidth for transmission.
Unicast mechanisms are therefore contrasted with broadcasting mechanisms which usually implies transmitting the same data to all possible destinations.
The 3rd Generation Partnership Project 3GPP has in TS 23.041 V11.0.0 standardized a Cell Broadcast Service CBS for GSM and UMTS.
The CBS service is analogous to the Teletex service offered on television, in that like Teletex, it permits a number of unacknowledged general CBS messages to be broadcast to all receivers within a particular region. CBS messages are broadcast to defined geographical areas known as cell broadcast areas. These areas may comprise of one or more cells, or may comprise the entire mobile network. CBS messages are broadcast cyclically by the cell at a frequency and for a duration agreed with the information provider.
GB-2 327 567 A provides a method wherein mobile stations' access to a limited access message transmitted using a cell broadcast service may be prevented by encrypting the message before transmission thereby providing message access only for authorized mobile stations.
A problem with GB-2 327 567 A is that it consumes a high level of the available amount of broad casting transmission resource as restricted by the available number of logical broadcast channels identified by Message Identifiers MI. For example, TS 23.041 V11.0.0 limits the number of MIs to two octets setting a limit of 65536 different codes. In practice this amount is further restricted by the 3GPP standard in that only the 1000 lowest MI codes may be entered by the user while the higher numbered codes require enablement by the network operator as set out in TS 23.041 V 11.0.0 Chapter 8.
In a large network where users are segmented into numerous groups due to for example hobbies, preferences or memberships in social networks—each requiring tailored notifications over cell broadcast—these limits are problematic for network operators.